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The number of stars in the Milky Way is relatively well known. We can measure the density of stars in the vicinity of the Sun and we can estimate how the light from stars changes with galactic radius. The Milky Way contains roughly 200,000,000,000 stars.

In the past few years, we have detected planets around many stars. But stable orbits about binary stars are almost impossible. (Over time, the planet would either be ejected into space, crash into one of the stars, or be thrown into a very eccentric orbit.)

Unless the two stars are very far apart, binary stars cannot have planets. This eliminates perhaps half the stars in the sky.

Radio waves are least effected by interstellar extinction. They also require the least energy to transmit (each photon has very low energy) and are easy to detect. We’ve been transmitting them for some time.

The atmosphere is transparent to radio waves. Light at these wavelengths can not only enter the Earth from space, but it can also depart the Earth for space.

Suppose there is at least 1 extra-terrestrial civilization out there that is more advanced than us by at least a few hundred years. Suppose at least one person in that civilization wants to be famous. He/She/It could …

Build a spaceship that could go to another star.

In 1977, NASA did this. They built two Voyager spacecrafts, which flew by Jupiter, Saturn, Uranus, and Neptune. In the 1990’s, these satellites passed the orbit of Pluto, and both will eventually reach nearby stars (in ~ 25,000 years).

Suppose there is at least 1 extra-terrestrial civilization out there that is more advanced than us by at least a few hundred years. Suppose at least one person in that civilization wants to be famous. He/She/It could …

Build a spaceship that could go to another star.

Program the spaceship/robots to look for a planet or an asteroid around that star

Voyager did this as well. While passing by the outer planets, it found many new moons.

Suppose there is at least 1 extra-terrestrial civilization out there that is more advanced than us by at least a few hundred years. Suppose at least one person in that civilization wants to be famous. He/She/It could …

Build a spaceship that could go to another star.

Program the spaceship/robots to look for a planet or an asteroid around that star

Suppose there is at least 1 extra-terrestrial civilization out there that is more advanced than us by at least a few hundred years. Suppose at least one person in that civilization wants to be famous. He/She/It could …

Build a spaceship that could go to another star.

Program the spaceship/robots to look for a planet or an asteroid around that star

Program the spaceship/robots to land and explore the object

Program the spaceship/robots to build an unmistakable sign, indicating the existence of the person

Program the spaceship/robots to use the materials on the planet to duplicate itself twice. The duplicates would then fly off to other stars and repeat the process.